C. 2nd Line of Defense of Innate Immunity

Question 1

2nd line of defense includes

Answer 1

complement system, phagocytes and coordinated response called inflammation. (also have role in adaptive immunity)

Question 2

complement system is composed of

Answer 2

set of inactive proteins found in blood and tissues

Question 3

fn of complement system

Answer 3

role in innate and adaptive immune systems. once activated undergo a catalytic cascade

Question 4

why are some labelled a and b eg C3a

Answer 4

cleavage of some of the complement components produces fragments that indicated by a and b

Question 5

cleavage of C3 produces

Answer 5

C3a + C3b

Question 6

the 3 complement pathways

Answer 6

alternate pathway which is part of the innate immunity. lectin pathway part of innate immunity. classical pathway part of adaptive immunity

Question 7

what are the diff btwn complement pathways

Answer 7

how they are activated and components that are used to produce a C3 convertase

Question 8

activation of the alternate pathway

Answer 8

small amount of C3b is always produced. in absence of bacterial cells, it is inactivated by Factor H.

Question 9

what happens if bacterial cells are presents during alternate pathway activation

Answer 9

C3b will bind to carbohydrate-containing surface structures like LPS and teichoic acids. triggers a series of events and production of enzyme called C3 convertase on surface of bacterial cells

Question 10

activation of the lectin pathway

Answer 10

lectin binds to specific CHO found on microbial surfaces such as MBL. ficolins bind acetylated sugars. binding of MBL or ficolin to pathogen surface activates the lectin pathway. results in formation of C3 convertase on surface of bac cell

Question 11

what are lectins

Answer 11

proteins that bind to CHO

Question 12

C3 convertase

Answer 12

C3 convertase of the alternative and lectin pathway cleaves lots of C3 into C3a + C3b. C3b will bind to bac surface and C3a diffuses away

Question 13

how is C5 convertase made

Answer 13

binding of C3b to a C3 convertase conversion

Question 14

C5 convertase

Answer 14

cleaves into C5a and C5b. C5b binds to bac surface; C5a diffuses away

Question 15

Membrane Attack Complex MAC

Answer 15

C5b bound to bac surface cause sequential binding of C6 C7 C8, conformational change exposes hydrophobic regions. they are inserted into membranes. copies of C9 added to complex forming a pore called MAC

Question 16

fn of MAC

Answer 16

lets lysozyme cross OM of gram -ive cells. thick layer of peptidoglycan does not allow insertion of MAC into PM of gram +ive

Question 17

C3b fn

Answer 17

surface bound C3b has role in phagocytosis as an opsonin, able to bind to both bac cell surfaces and phagocytes. phagocytes have C3b receptors. binding of C3bR to C3b on bac surface enhances phagocytosis

Question 18

C3a and C5a fn

Answer 18

diffused away from cell, called anaphylatotoxins and have role in inflammation

Question 19

vasodilation

Answer 19

dilation of blood.

Question 20

how does the capillaries dilate

Answer 20

C3s and C5a bind to their recpetors on capillary endothelial cells. vasodilation occurs increasing blood flow to area, now warm and red. also causes blood flow rate to decrease helping neutrophils and other cells bind to endothelium

Question 21

C3s and C5a also cause capillaries to be leaky, why important

Answer 21

increases movement of plasma and solubilized proteins out of blood. excess fluid in tissues cause swelling, called edema. leakiness facilitates neutrophil diapedesis

Question 22

mast cells are

Answer 22

type of leukocyte associated with skin, connective tissue and muscosa. they have recpetors for C3a and C5a.

Question 23

how is histamine releases

Answer 23

mast cell C3a and C5a receptors binding to C3a and C5a releasing histamine.

Question 24

histamine

Answer 24

also contributes to vasodilation and leakiness of nearby capillaries

Question 25

C3a and C5a also fn as

Answer 25

chemoattractants. they attract phagocytes to an infect area. eg CXCL8